1. Field of the Invention
The present invention relates to a thin film magnetic head which can be fabricated with the aid of thin film forming means for forming thin films through plating, vapor deposition, sputtering or the like and a high precision pattern forming means referred to as photolithography.
2. Description of the Prior Art
The magnetic head whose magnetic circuit is implemented with the aid of the thin film technology is generally considered advantageous in that the recording density can be enhanced and increasingly tends to replace the magnetic head of the type in which a coil is wound on a ferrite or permalloy piece. A typical structure of such thin film head is described in detail in Japanese Patent Application Laid-Open No. 84020/80 which corresponds to U.S. Pat. No. 4,219,854. For attaining an increased data recording density with the magnetic circuit of the thin film magnetic head, it is a fundamentally important factor to reduce the thickness of a magnetic layer exposed on an air bearing surface and hence the thickness of a pole piece of the magnetic head. However, in case one and the same magnetic head is destined to serve for both recording and reading data on and from a recording medium, thinning of the pole piece as described above can never be the necessary and sufficient condition for attaining the increased recording density. More specifically, upon recording operation, it is necessary to excite the magnetic circuit by causing an exciting current to flow through the conductor coil to thereby generate a desired magnetic field in the recording medium which is disposed with a predetermined gap from the air bearing surface of the magnetic head. In this connection, the magnetic layer of a reduced thickness is readily magnetically saturated and therefore an increased exciting current can not produce the effective magnetic field. Under the circumstances, it is important to determine the range of the thickness of the magnetic layer which satisfies the conditions for assuring both the recording and the reading operations in a satisfactory manner. At present, however, the prevailing trend is toward the imparting of a high coercive force to the recording medium in an effort to attain the high recording density, which means that the magnetic head has to be capable of producing a magnetic field of a correspondingly increased strength. To meet this requirement, the range of the thickness of the magnetic layer in which both the recording and the reading operations can be effected satisfactorily is inevitably significantly narrowed and, in a extreme case, such thickness range will become actually no more available, giving rise to a serious problem to be dealt with.